To Spray or Not to
Spray?Pesticide Spraying for Mosquitoes that
Carry West Nile Virus Did
NOT Contaminate People

June 10, 2005

Mosquitoes carry a variety of diseases that can be transmitted to humans.
West Nile virus, a mosquito-borne disease that
affects the nervous system, has spread to almost every state in the US.
To control mosquitoes, officials sometimes spray pesticides to kill the
insects. Some people worry that exposure to pesticides can cause human
health problems. Three recent studies should help calm these fears:
they show that people in areas sprayed with pesticides to control
mosquitoes did not have elevated levels of
pesticides.

Study 1: Mississippi, 2002

Results: The urine levels of pesticide metabolites in people inside and
outside of the spray area were not statistically
different. However, people who used pesticides on their pets had higher
levels of pesticide metabolites in their urine than those people who did
not use pesticides on their pets.

Study 2: North Carolina, 2003

Why spray: Mosquito populations were expected to increase after the
heavy rains brought by Hurricane Isabel in 2003.
What sprayed: Ultra-low volume spraying of the pesticides naled
and permethrin.
Who tested: 75 people inside of the spray area who provided urine samples
before and after the spraying.

Results: People inside of the spray area did not have
increased levels of pesticide metabolites in their urine. However, people
who worked on farms or handled pesticides as part of their jobs had higher
pesticide levels than those people who did not work on farms or handle
pesticides.

Study 3: Virginia, 2003

Why spray: Mosquito populations were expected to increase after the
heavy rains brought by Hurricane Isabel in 2003.
What sprayed: Ultra-low volume spraying of naled and d-phenothrin.
Who tested: 83 people inside of the spray area who provided urine samples
before and after spraying.

Results: There was no difference in the amounts of
pesticide metabolites
in the urine of people tested before and after spraying.

The results of these three studies are a breath of fresh air to those who
were concerned about the dangers of spraying the pesticides. Long-term
exposure to naled, permethrin and d-phenothrin can cause skin,
respiratory, digestive and nervous system problems. However, as these
studies show, the ultra-low volume spraying of these pesticides did not
appear to cause increased levels of the pesticides in people who lived in
the sprayed areas. This is good news to people who live in areas with
mosquitoes carrying West Nile virus.

Pesticides Used

Naled:
an organophosphate pesticide; kills adult mosquitoes; sprayed from
aircraft or by trucks; inactivates the enzyme that breaks down the neurotransmitter
acetylcholine.

d-Phenothrin - a
synthetic pyrethoid, similar to a chemical found in chrysanthemum flowers;
kills adult mosquitoes; sprayed from trucks; disrupts sodium channels on
nerve axons.